1. Field of the Invention
The present invention relates to an illuminating optical system, and a projection type display apparatus employing the illuminating optical system.
2. Description of the Related Art
(Background)
In recent years, a projection apparatus (projection type display apparatus) has been highlighted as an image display apparatus for a large screen. Products available as such projection apparatuses include a CRT (Cathode Ray Tube) projection apparatus employing a small-sized CRT of high definition and high luminance, a liquid-crystal projection apparatus employing a liquid crystal panel, a DMD (Digital Micromirror Device) projection apparatus employing a DMD, etc.
Further, a category called xe2x80x9cdata projectorxe2x80x9d which, not only copes with AV sources such as a motion picture and a TV program, but also projects a computer image, is rapidly spreading its market. The performances of the data projector, such as the brightness, contrast and resolution of a projected image and uniformity in the brightness, have been remarkably enhanced.
The projection apparatus employing a light valve, such as the liquid crystal panel or the DMD, is superior to the CRT projection apparatus especially due to the fact that a brightness and a resolution can be enhanced independently of each other. Accordingly, the light-valve projection apparatuses are being increasingly applied to projection television sets (rear projection type projectors).
Most of known light-valve illuminating optical systems have been based on a kind of Kxc3x6hler""s illumination wherein the light valve is arranged and illuminated in the optical path of a lens system in which a light source and the exit pupil of a projecting lens are held in a conjugate relationship.
In recent years, however, fly-eye integrator illumination or rod integrator illumination has been often employed for enhancing uniformity in illumination, and a demand has been made for an optical system which has a higher level of image forming performance and a more complicated architecture as compared with the illuminating optical system.
(Related Art)
FIG. 6 shows a related art reflection type projector disclosed in the official gazette of Japanese Patent No. 2,939,237. Referring to the figure, numeral 110 designates a lamp house which generates light and causes it to emerge therefrom, and which is configured of a lamp 111 and a reflector 113.
Numeral 120 designates a color wheel through which the light emergent from the lamp house 110 is selectively transmitted depending upon wavelengths, and which includes a color filter 121 adapted to be rotated by a driver 123. The projector also comprises light mixing means 130 for diverging/converging or irregularly reflecting the light having entered from the side of the lamp house 110, so as to turn it into uniform light, a relay lens unit 140 which converges the entering light and turns it into parallel light rays, a critical angle prism 150 which reflects light reflected from image generation means 160 and then having entered into this prism again, and a projection lens unit 170 which magnifies entering light rays and transmits them toward a screen.
As a practicable example of the light mixing means 130, a scrambler 135 is arranged in the illustration. The scrambler 135 forms a rectangular parallelepiped (alternatively, a regular hexahedron) out of an entrance surface 135a which is perpendicular to an optical path and which is located at the point of convergence of the light emitted from the lamp 111, an exit surface 135b which is also perpendicular to the optical path, and four side surfaces. More specifically, the exit surface 135b is in the shape of an oblong and has an aspect ratio which corresponds to that of an FLCD (Ferroelectric Liquid Crystal Display) 163 forming the image generation means 160. The non-uniform light rays emergent from the lamp house 110 are mixed by the scrambler 135 into the uniform light, which is caused to exit from the exit surface 135b. The relay lens unit 140 is configured of a converging lens 141 for diverging the uniform light, and a collimator lens 143 for converging the entering divergent light rays into the parallel light rays, by which the FLCD 163 is illuminated.
In the illustrated architecture, the image generation means 160 is formed of the FLCD 163, and hence, a polarizer 161 and an analyzer 165 are disposed before and behind the FLCD 163.
According to the construction of the related art example, it is possible to provide the reflection type projector which changes the traveling path of the light by adopting the critical angle prism, thereby excluding the adoption of a polarizing beam splitter, and in which the optic axis alignment of the optical system is facilitated without requiring a great optical length. Besides, according to the so-called xe2x80x9crod integrator illuminationxe2x80x9d employing light mixing means such as a scrambler 135, the architecture of an optical system is simplified, and it is possible to provide an illuminating optical system and a projection apparatus of excellent cost performance.
An object of the present invention is to provide an illuminating optical system in which non-uniformity in the intensity of light emitted from a light source is relieved to enhance uniformity in the brightness of an illuminating light beam, and in which an illumination margin is decreased to heighten the utilization factor of light, and a projection apparatus in which the illuminating optical system is mounted.
An illumination apparatus according to the present invention is characterized by comprising focusing means for focusing light emitted from a light source; columnar optical means having its light entrance portion located in the vicinity of a position where the emitted light is focused by the focusing means, and for propagating the entering light having entered from the light entrance portion and causing the propagated light to exit from its light exit portion; and transferring optical means including a first group of lenses which receive the exiting light from the columnar optical means and which have a positive refracting power, a second group of lenses which receive exiting light from the first group of lenses and which have a positive refracting power, and a third group of lenses which receive exiting light from the second group of lenses and which have a positive refracting power, wherein the respective groups of lenses are successively arrayed from a side of the columnar optical means toward a side of a surface to-be-illuminated and satisfy relationships of inequalities (1) and (2) given below, and wherein the light exit portion of the columnar optical means and the surface to-be-illuminated are held in a conjugate relationship;
0.37 less than f1/f0 less than 0.62xe2x80x83xe2x80x83(1) 
"ugr"p/"ugr"n greater than 1.99xe2x80x83xe2x80x83(2) 
where
f0: focal length of the transferring optical means,
f1: focal length of the first group of lenses,
"ugr"p: means Abbe number of a positive lens included in the second group of lenses, and
"ugr"n: means Abbe number of a negative lens included in the second group of lenses.
Besides, a projection type display apparatus according to the present invention is characterized by comprising a light source; focusing means for focusing light emitted from the light source; columnar optical means having its light entrance portion located in the vicinity of a position where the emitted light is focused by the focusing means, and for propagating the entering light having entered from the light entrance portion and causing the propagated light to exit from its light exit portion; transferring optical means including a first group of lenses which receive the exiting light from the columnar optical means and which have a positive refracting power, a second group of lenses which receive exiting light from the first group of lenses and which have a positive refracting power, and a third group of lenses which receive exiting light from the second group of lenses and which have a positive refracting power, wherein the respective groups of lenses are successively arrayed from a side of the columnar optical means toward a side of a surface to-be-illuminated and satisfy relationships of inequalities (1) and (2) given below, and wherein the light exit portion of the columnar optical means and the surface to-be-illuminated are held in a conjugate relationship; optical-path deflection means receiving light exiting from the transferring optical means, and for deflecting the exiting light in a direction different from an entering direction thereof; light modulation means disposed at a position of the surface to-be-irradiated so as to receive the exiting light from the transferring optical means after the deflection by the optical-path deflection means, and for modulating the exiting light in two dimensions so as to generate modulated light; and projection means for projecting the modulated light generated by the light modulation means;
0.37 less than f1/f0 less than 0.62xe2x80x83xe2x80x83(1) 
"ugr"p/"ugr"n greater than 1.99xe2x80x83xe2x80x83(2) 
where
f0: focal length of the transferring optical means,
f1: focal length of the first group of lenses,
"ugr"p: means Abbe number of a positive lens included in the second group of lenses, and
"ugr"n: means Abbe number of a negative lens included in the second group of lenses.